I think you're reading a little too much into it. Steam solved this "problem" long ago.

Optical drives may eventually become less common. I admit mine rarely gets much use, but I still fancy throwing a DVD in there once and a while.

But that does present an interesting problem if you're, say, Microsoft. How do you sell Word to someone who doesn't have an optical drive? Would Microsoft or Adobe or anyone else who sells big-ticket shrink-wrapped software turn to the App Store to solve that problem? Not in a million years.